316 - Stainless steel - Hexagon socket cap screw

Technical Superiority of Grade 316 (A4)

While Grade 304 (A2) is suitable for general use, Grade 316 (A4) is engineered for the extremes. The socket cap design allows for high-torque tightening in compact spaces, while the A4 material ensures the fastener remains structurally sound even after years of exposure to salt spray or chemical cleaning agents. This makes it the standard specification for critical sub-sea and coastal engineering.

Material Specifications: A4-70

Our inventory consists primarily of A4-70 grade fasteners, defined by the following characteristics:

Molybdenum Content (2-3%)

This is the key chemical difference. The addition of molybdenum drastically improves the steel's resistance to "pitting" – microscopic holes that form on the surface of metals in chloride-rich environments like ocean water.

Mechanical Strength (Class 70)

Tensile Strength: Minimum 700 N/mm². Provides reliable load-bearing capacity for structural components. Yield Strength: Minimum 450 N/mm². Ensures the bolt retains its elasticity and clamping force under load.

Non-Magnetic Properties

Grade 316 has lower magnetic permeability than Grade 304, making it the preferred choice for sensitive electronic instrumentation and medical devices where magnetic interference must be minimized.

Quality Assurance

When you pay for premium alloy, you deserve proof of quality. We can provide an EN 10204 3.1 Material Certificate upon request, verifying the molybdenum content and mechanical properties of your batch. Please note that third-party inspection services require an additional fee.

Critical Applications

Grade 316 plain head socket screws are the "go-to" fastener for rigorous industries:

• Marine Hardware: Deck fittings, instrument mounting, and engine components on yachts and commercial vessels.
• Chemical Processing: Flange connections and pump assembly in plants handling aggressive fluids.
• Pharmaceuticals: Clean-room machinery where frequent sterilization with harsh chemicals occurs.
• Coastal Architecture: Outdoor lighting and structural fixings located within 5km of the coastline.

Frequently Asked Questions

Why choose a Plain head for marine use?

In marine environments, salt crystals and grime can accumulate in the textured surface of a knurled head, accelerating corrosion or causing staining. A plain (smooth) head allows water to run off easily and can be wiped clean instantly, reducing maintenance requirements.

Do I need to lubricate 316 socket screws?

Yes, lubrication is highly recommended. Stainless steel threads, particularly the higher alloyed 316 grade, are prone to "galling" (cold welding) during installation. Applying a high-quality anti-seize paste (like Nickel or Moly) prevents the threads from locking up permanently.

Is A4-80 stronger than A4-70?

Yes. A4-80 has a tensile strength of 800 N/mm², whereas A4-70 is 700 N/mm². While A4-70 is the standard stock item suitable for most applications, A4-80 is used for high-stress structural connections. Currently, our online listing focuses on standard A4-70, but please contact us if you require high-strength A4-80 specifically.